Reflecting real-world patients with mesothelioma in research: an interim report of baseline characteristics from the ASSESS-meso cohort

Mesothelioma varies in clinical phenotype and survival. Clinical trials are unavoidably affected by selection bias, reducing generalisability. ASSESS-meso is a UK, multi-centre, prospective, mesothelioma cohort study (ISRCTN61861764). This pre-specified interim analysis, conducted when recruitment reached 25% of target, summarised participant characteristics and evaluated external validity through comparison with real-world and clinical trial cohorts.The study took place at 14 hospitals across the UK. People diagnosed with mesothelioma, at any anatomical site, were eligible. Clinical, radiological and biochemical data were collected at enrolment. In this interim report, the external validity of the cohort was investigated through comparison of baseline demographic data with populations included in the 2020 UK National Mesothelioma Audit (real-world cohort), and CHECKMATE-743 and MAPS trials (clinical trial cohorts).Between 07/04/2017–01/03/2022, 244 patients were enrolled. The cohort was predominantly male (195/244; 80%) with median age of 74 years. Pleural disease and epithelioid sub-types were most prevalent. ASSESS-meso participants were more similar to the real-world population with regards age, performance status, disease site and stage than the clinical trial population. ASSESS-meso participants were more likely to be formally staged and less likely to have undifferentiated histology compared with the real-world cohort, possibly reflecting high rates of discussion of ASSESS-meso participants at regional mesothelioma MDTs. As expected, poorer performance status, non-epithelioid histology and neutrophil-lymphocyte ratio were associated with shorter survival in the adjusted analysis.ASSESS-meso is representative of the UK mesothelioma population. Future outputs from the cohort will help characterise different mesothelioma phenotypes with high external validity.